Supplying liquid to a vacuum chamber

ABSTRACT

Liquid is supplied to a receptacle in a vacuum chamber through a barometric leg, the outer end of which dips into a feed chamber. This chamber is interconnected with a reservoir by filling means including a pump and draining means arranged to maintain a flow of liquid between reservoir and feed chamber. Means are provided to maintain a constant liquid level in the feed chamber.

[56] References Cited UNITED STATES PATENTS Inventors Joseph Paul Gimigliano Pittsburgh; John Francis Butler, Bethel Park, both of Pa.

United States Patent 164/156X 137/5 77X 164/257X 1 18/491 1 18/49X 1 18/49X Barstow et a1.

954 Hoffmann 962 Chambers 962 Baughman et a1.

968 Ashburn et a1.

969 Ashburn.......................

Primary ExaminerWilliam R. Cline Attorney-G. R. Harris (21] Appl. No. 749,741

[22] Filed I Aug. 2, 1968 (45] Patented June 1,1971

[73] Assignee Jones 8: Laughlin Steel Corporation Pittsburgh, Pa.

pplied to a receptacle in a vacuum etric leg, the outer end ofwhich dips mber is interconnected with a pump and draining iquid between reservoir provided to maintain a constant ABSTRACT: Liquid is su chamber through a barom into a feed chamber. This cha reservoir by filling means including a means arranged to maintain a flow of l and feed chamber. Means are liquid level in the feed chambe AMBER [54] SUPPLYING LIQUID TO A VACUUM CH 8 Claims, 4 Drawing Figs.

137/577, 118/7, 118/49,164/15 [51] lnt.Cl........ [50] FieldoiSearch...................... 565,577; 117/107, 119;118/7, 8,49,49]; 164/15 7 I 6 ////V v/ vv PATENTED JUN 1 ran SHEET 1 OF 3 Fig. I

INVENTOR.

JOSEPH P. cnmcumo and JOHN F. BUTLER Fig.2

ATTORNEY PATENTEIJIJUN Men 3581; 706

SHEET 2 0F 3 INVENTORS JOSEPH R GIMIGLIANO JOHN F. BUTLER their ATTORNEY PATENIED JUN 1 Ian llll Fig.4.

INVENTORS JOSEPH P. GIMIGLIANO JOHN F. BUTLER their ATTORNEY SUPPLYING LIQUID TO A VACUUM CHAMBER In the continuous vacuum vapor coating of a liquid substance on an elongated substrate, the substrate is continuously moved through a vacuum chamber in which the liquid substance is vaporized and thereafter condensed on the substrate. Such a process is adapted for the continuous vacuum vapor coating of a metal substrate with a coating metal ofa different metal, for example, a steel substrate with a coating of aluminum, zinc or the like. Obviously, such a process requires replenishment of the supply of coating substance, and it is advantageous to supply the coating substance continuously to the evaporation receptacle. It is further advantageous to supply the coating substance at the same rate as it is vaporized so that steady-state heat flow conditions are maintained in the evaporation receptacle. As the evaporation receptacle is in the evacuated chamber, the level of the liquid substance therein is not readily available for control purposes.

It is an object of our invention, therefore, to provide apparatus for continuously supplying liquid to a receptacle in an evacuated chamber at the same rate the liquid is vaporized therein. It is another object to provide such apparatus which is positioned entirely outside the evacuated chamber. It is still another object to provide such apparatus which has no control elements within the evacuated chamber. It is a further object to provide a means for rapidly filling and emptying a receptacle within an evacuated chamber. It is yet another object to provide a method of handling a liquid substance containing a heavier impurity which does not vaporize with the principal constituent. Other objects of our invention will become apparent from the description thereof which follows.

Embodiments of our invention presently preferred by us are illustrated in the accompanying figures to which reference is now made.

FIG. I is a vertical schematic section ofa first preferred embodiment of our invention.

FIG. 2 is a vertical schematic section ofa second preferred embodiment.

FIG. 3 is a vertical schematic section, in somewhat more detail than FIGS. 1 and 2, ofa third preferred embodiment.

FIG. 4 is a vertical schematic section of a portion of a fourth preferred embodiment.

Our apparatus causes the liquid to flow into the evaporation receptacle in the evacuated chamber by means of the pressure of the atmosphere over the liquid in a liquid feed chamber. This chamber is interconnected with a liquid reservoir so that the level of the liquid in the feed chamber is maintained constant. We describe our apparatus hereinafter as it is adapted to supply molten metal.

In FIG. I the evacuated chamber 1, which is indicated only in part because it is conventional, is provided with an evaporation receptacle 2, which is also conventional. Evaporation receptacle 2 is heated by heating means, not shown. Leading from the evaporation receptacle 2 is a pipe 3 which passes through the wall of vacuum chamber I through a vacuum seal 4. Pipe 3 is inclined slightly downwardly so that it serves to drain evaporation receptacle 2. The end of pipe 3 outside vacuum chamber 1 connects with a vertical leg I5 which extends downwardly into a liquid feed chamber 5, the top of which is open to the atmosphere. Feed chamber 5 is contained within a larger liquid reservoir 6. At the bottom of feed chamber 5 is provided an orifice 7 which opens into reservoir 6 so that it serves as a means for draining feed chamber 5 into reservoir 6. A liquid pump 8 is positioned with its intake 9 within reservoir 6 at a location below the normal level of liquid in reservoir 6. Pump 8 is provided with a motor 10 which is connected to a source of power, not shown. Pump 8 is provided with a discharge pipe 11 which extends upwardly and over the edge of feed chamber 5 in an inverted U." The outside leg 12 of discharge pipe 11 extends into feed chamber S'to a position below the normal level of the liquid in feed chamber 5. Reservoir 6 is provided with a drain I3 which is nonnally closed. Reservoir 6 is surrounded by a furnace 14.

Within feed chamber 5 is positioned a liquid level sensing device 16. This device 16, which is conventional, is connected to the pump motor I0 through wires 17 and conventional proportioning means, not shown. These means increase or decrease the speed of pump motor 10 in response to the signal from the level sensing device 16.

The operation of our apparatus as illustrated in FIG. I will be apparent from the foregoing description. The distance between the normal surface of liquid in evaporation receptacle 2 and a chosen level of the liquid in feed chamber 5 is determined by the difference between the atmospheric pressure over the liquid in feed chamber 5 and the pressure over the liquid within vacuum chamber I. This distance is equal to the height of the column of the liquid which is supported by that pressure. If the level of the liquid in feed chamber 5 is maintained constant at its predetermined position, the level of the liquid in evaporation receptacle 2 will likewise remain constant because the atmospheric pressure will cause liquid to flow up pipe 15 and over through pipe 3 into evaporation receptacle 2 whenever the level of the liquid in receptacle 2 falls. The level of the liquid in reservoir 6 is normally below that of the liquid in feed chamber 5, and the function of pump 8 is to keep the level of the liquid in feed chamber 5 constant. This is effected by level-sensing device 16 which has been described. When the level of the liquid in feed chamber 5 falls, the liquid-sensing device 16 causes pump 8 to increase its pumping speed and draw more liquid from reservoir 6 through the pump intake 9 and discharge it through pump discharge II into feed chamber 5. The liquid in feed chamber 5 is constantly draining through orifice 7 back into reservoir 6 so that the liquid circulates between reservoir 6 and feed chamber 5. From time to time the liquid in reservoir 6 is replenished. When the liquid to be evaporated is a liquid metal, it must, of course, be kept above its melting point, and this heating is accomplished by furnace 14 which surrounds reservoir 6 and feed chamber 5. i

In the embodiment of our invention shown in FIG. 2, the elements which are the same as those in FIG. I are indicated by the same reference characters. In FIG. 2 the reservoir 20 is provided with a feed chamber 2| at one end, the feed chamber 21 having a bottom which is lower than that of reservoir 20. An orifice 22 is provided in wall 23 which partitions feed chamber 21 from reservoir 20 so that liquid constantly drains from reservoir 20 into feed chamber 21. Pump 8 is located with its intake 9 in feed chamber 21 and its discharge pipe 12 in reservoir'20. The difference between the apparatus of the two figures is, of course, that the level of the liquid in the reservoir 20 of FIG. 2 is higher than the normal level of the liquid in the feed chamber 21 whereas in FIG. 2 the normal level of the liquid in reservoir 6 is below that of the liquid in feed chamber 5. Thus, in FIG. 2 the liquid flows by gravity from reservoir 20 into feed chamber 21 through orifice 22 and is pumped out of feed chamber 21 back into reservoir 20 by pump 8. Otherwise, the apparatus of our FIG. 2 operates the same way as that of our FIG. I.

In the embodiment of our invention shown in FIG. 3, the elements which are the same as those of FIG. I are indicated by the same reference characters. In FIG. 3, feed chamber 24 is elevated above reservoir 6 and is adapted to be located at a distance therefrom, as will be hereinafter described. Feed chamber 24 is constructed of, or is lined with, heat insulating material. Through and below the bottom of feed chamber 24 extends a drain tube 29 which is provided with a heat insulating outer lining 31. The lower end of tube 29 is connected to an extension 30 which is constructed of or is lined with heat insulating material. The lower end of extension 30 projects into reservoir 6. A movable sleeve 32 is adjustably positioned in drain tube 29 and extends above its upper end so that the upper end of sleeve 32 can be adjusted to a desired height. This sleeve forms an overflow drain through which the liquid flows out of feed chamber 24. The level of the liquid in feed chamber 24 cannot rise above the level of the upper end of adjustable sleeve 32. Pump 8, which is otherwise positioned as is shown in FIG. 1, is provided with a discharge tube 26 having a heat-insulating lining 28. The upper end of discharge tube 26 is bent over into a downwardly extending discharge end 34 which projects into feed chamber 24 well below the upper end of sleeve 32.

Crucible 2 within vacuum chamber 1 is provided as before with a drain tube 3 which is connected to a downwardly extending section 15 having an insulated covering 27. If necessary, conventional heating means are interposed between tube 15 and insulating covering 27. The lower end of tube 15 is bent to a vertical downwardly projecting element 25 which extends into feed chamber 24 well below the level of the top of sleeve 32.

The operation of the apparatus of FIG. 3 is generally similar to that of the embodiments of FIGS. 1 and 2 which have been described. Pump 8 runs constantly and pumps liquid from reservoir 6 through pump discharge tubes 26 and 34 into feed chamber 24. This liquid fills the feed chamber to the level of the upper end of sleeve 32 and overflows through that sleeve and its extensions 31 and 30 back into reservoir 6. The level of the liquid in feed chamber 24 is predetermined by the spacing of the upper end of sleeve 32 from the bottom of feed chamber 24. Liquid from chamber 24 is forced upwardly through tubes 25, 27 and 3 into crucible 2 in vacuum chamber 1 by the difference in pressure between that on the surface of the liquid in chamber 24 and the reduced pressure in vacuum chamber 1.

Our apparatus illustrated in FIG. 3 is particularly well adapted to installations in which more than one crucible must be supplied, or an elongated crucible must be supplied with liquid at more than one point. FIG. 3 illustrates only one feed chamber 24, but the apparatus as there shown is suitable for use with several feed chambers 24, all of which are supplied with liquid metal by the same pump 8 from the same reservoir 6 and each of which supplies liquid to its crucible through its own barometric leg feed tube arrangement.

Our apparatus illustrated in FIG. 3 is also particularly well adapted for rapid filling or emptying of the evaporation receptacle. Feed chamber 24 is not connected to crucible 2, to reservoir 6, or to pump 8 and its associated pipes, except as pipes 25 and 34 dip into the coating material held in feed chamber 24, and drain 30 therefrom dips into coating material held in reservoir 6. Lowering feed chamber 24 therefore causes coating material to flow from crucible 2 through pipes 3, l and 25 into feed chamber 24. Raising feed chamber 24 causes coating material to flow from it through pipes 25, I5 and 3 into crucible 2.

In each of the three embodiments of our invention which we have described, the feed chamber is open to the atmosphere. This construction requires that the feed chamber be positioned below the crucible the full length of the barometric leg for the liquid supply. Under some circumstances this arrangement may not be convenient. If it is desired to bring the feed chamber closer to the crucible, for example, in the embodiment shown in FIG. 3, the feed chamber is enclosed and maintained at a pressure intermediate the pressure in the evacuated chamber and atmospheric pressure. The difference in pressure between feed chamber and reservoir will then have to be taken into account in positioning the reservoir below the feed chamber.

The essential elements of this fourth embodiment of our invention are illustrated in FIG. 4. Those elements in FIG. 4 which are also found in FIG. 3 are identified by the same reference characters. The feed chamber 24 which is otherwise identical to feed chamber 24 of FIG. 3 is provided with a cover 33 through which pipes 25 and 34 are lead in. Cover 34 is also provided with an exhaust pipe 35 which is connected to pumping means, not shown, to reduce the pressure within chamber 24 to a desired value above that in vacuum chamber 1. As before, molten coating material from reservoir 6 is supplied to feed chamber 24 through pipe 34. Molten metal from feed chamber 24 is caused to flow from it upwardly through pipe 25 into crucible 2 because the pressure maintained in feed chamber 24 is greater than that in vacuum chamber 1.

Our apparatus, particularly as it is shown in FIGS. I and 2 hereof and described in connection therewith, enables us to vaporize and condense without difficulty certain substances which heretofore have presented problems. These are substances contaminated with impurities which do not vaporize in substantial amounts at the evaporation temperature of the major constituent but which build up in concentration in the evaporation receptacle. Perhaps the most commercially important substance of this nature is zinc which contains lead in small amounts. Lead does not vaporize in significant amounts at zinc evaporation temperatures but remains in the evaporation receptacle. As its concentration approaches 2 percent, it separates into a heavier phase which sinks to the bottom of the receptacle. In our apparatus as shown in FIG. 1 this heavier phase drains through feed pipes 3 and 15 back into feed chamber 5 and eventually through aperture 7 from that feed chamber into reservoir 6. From reservoir 6 it is removed from time to time through drain I3. This draining out from evaporation receptacle 2 is continuous and goes on simultaneously with the continuous supplying of fresh molten metal through feed pipes 3 and 15.

We claim:

I. Apparatus for supplying a liquid to an evaporation receptacle enclosed in a vacuum chamber comprising a liquid reservoir open to the circumambient atmosphere positioned outside the vacuum chamber, a feed chamber positioned outside the vacuum chamber, filling means including a pump interconnecting the liquid reservoir and the feed chamber and draining means interconnecting the liquid reservoir and the feed chamber, the filling means and the draining means being adapted and adjusted to maintain a circulating flow of liquid between liquid reservoir and feed chamber, a feedpipe having its lower end positioned in the feed chamber rising therefrom and extending through a wall of the vacuum chamber into the evaporation receptacle and control means positioned in the feed chamber adapted to maintain a constant level of liquid therein, the feed chamber being positioned below the evaporation receptacle a distance such that the levels of the liquid in them differ by the height of the column of the liquid supported by the pressure of the atmosphere in the feed chamber less the pressure of the atmosphere in the vacuum chamber.

2. Apparatus of claim I in which the feed pipe slopes so as to drain the liquid out of the evaporation receptacle and back into the feed chamber.

3. Apparatus of claim 1 including heating means surrounding the liquid reservoir.

4. Apparatus of claim 1 in which the feed chamber is open to the circumambient atmosphere.

5. Apparatus of claim 1 in which the reservoir is positioned at a higher level than the feed chamber and the draining means comprise an orifice in the bottom of the reservoir through which the liquid drains therefrom into the feed chamber, and the liquid pump is positioned with its intake in the feed chamber and discharge in the reservoir so as to pump liquid from the feed chamber into the reservoir.

6. Apparatus of claim 1 in which the control means comprise liquid level sensing means, and including means actuated by the liquid level sensing means adapted to control the operation of the pump.

7. Apparatus of claim 1 in which the feed chamber is positioned so as to permit vertical movement thereof with respect to to the liquid reservoir and the evaporation receptacle.

8. Apparatus of claim 1 in which the feed chamber is closed and is maintained at a pressure intermediate the circumambient atmospheric pressure and the pressure of the atmosphere in the vacuum chamber. 

1. Apparatus for supplying a liquid to an evaporation receptacle enclosed in a vacuum chamber comprising a liquid reservoir open to the circumambient atmosphere positioned outside the vacuum chamber, a feed chamber positioned outside the vacuum chamber, filling means including a pump interconnecting the liquid reservoir and the feed chamber and draining means interconnecting the liquid reservoir and the feed chamber, the filling means and the draining means being adapted and adjusted to maintain a circulating flow of liquid between liquid reservoir and feed chamber, a feedpipe having its lower end positioned in the feed chamber rising therefrom and extending through a wall of the vacuum chamber into the evaporation receptacle and control means positioned in the feed chamber adapted to maintain a constant level of liquid therein, the feed chamber being positioned below the evaporation receptacle a distanCe such that the levels of the liquid in them differ by the height of the column of the liquid supported by the pressure of the atmosphere in the feed chamber less the pressure of the atmosphere in the vacuum chamber.
 2. Apparatus of claim 1 in which the feed pipe slopes so as to drain the liquid out of the evaporation receptacle and back into the feed chamber.
 3. Apparatus of claim 1 including heating means surrounding the liquid reservoir.
 4. Apparatus of claim 1 in which the feed chamber is open to the circumambient atmosphere.
 5. Apparatus of claim 1 in which the reservoir is positioned at a higher level than the feed chamber and the draining means comprise an orifice in the bottom of the reservoir through which the liquid drains therefrom into the feed chamber, and the liquid pump is positioned with its intake in the feed chamber and discharge in the reservoir so as to pump liquid from the feed chamber into the reservoir.
 6. Apparatus of claim 1 in which the control means comprise liquid level sensing means, and including means actuated by the liquid level sensing means adapted to control the operation of the pump.
 7. Apparatus of claim 1 in which the feed chamber is positioned so as to permit vertical movement thereof with respect to to the liquid reservoir and the evaporation receptacle.
 8. Apparatus of claim 1 in which the feed chamber is closed and is maintained at a pressure intermediate the circumambient atmospheric pressure and the pressure of the atmosphere in the vacuum chamber. 